In the welding industry, tremendous numbers of robotic welding stations are operable to draw welding wire from a package as a continuous supply of wire to perform successive welding operations. The advent of this mass use of electric welding wire has created a need for large packages for containing and dispensing large quantities of welding wire. However, as can be appreciated, there is a limit to the size of the welding wire package. If the packages or containers are too large, they become difficult to transport and are very costly. These can be factors if the container is damaged. In addition, the container consumes a large portion of floor space near the welding operation. As a result, even when large containers of welding wire are utilized, downtime is inevitable when the wire is exhausted from the container. While quick changeover techniques can be utilized to replace the exhausted container with a new container of welding wire, the welding operation is shut down. In view of the new high-tech and costly robotic welding systems, a short downtime can be very costly. This is especially true in multiple robotic welding production lines that utilize several robotic welding operations. As can be appreciated, a single offline robotic welder can result in several robotic welding systems being forced offline.
In order to reduce downtime, attempts have been made to link the welding wire from one container to the welding wire of another container. Theoretically, if welding wire containers can be joined to one another, an “endless wire” welding wire supply can be produced, wherein a welding operation is never shut down due to an exhausted wire container. While this theory is sound, the practicality of achieving an endless wire without tangling the welding wire is a different matter. As can be appreciated, a tangled welding wire can be an even worse condition than an exhausted container of welding wire and can create greater amounts of downtime. Accordingly, in order to achieve an endless wire container, tangling needs to be eliminated, or at least made a rare occurrence.
A large capacity welding wire container typically includes an outer container, such as a drum, with welding wire looped about a central, vertical axis to form a wire coil. The coil has a top surface with an outer cylindrical surface that is supported by the outer packaging and an inner cylindrical surface defining a central bore coaxial to the central, vertical axis. The central bore can be occupied by a cardboard, cylindrical core, as is shown in Cooper U.S. Pat. No. 5,819,934.
Jensen discloses an endless wire arrangement used in connection with octagonal welding wire containers. With reference to FIGS. 1C and 1D, Jensen further discusses the e-script condition that results when the welding wire from one container is joined to the welding wire of another container. As is stated above, the welding wire is wound into the container such that it extends about a vertically extending central axis. Further, the winding process can be used to produce a natural cast in the wire, creating upward spring forces in the coil and an outward force in the coil. As the wire is exhausted in the one container, the last remaining loop rises in the container and folds over itself to produce the e-script tangle. As can be appreciated, the e-script tangle forces the operation to be shut down so that the e-script can be removed.
Jensen attempts to overcome the e-script problem with a large, bulbous runner 11. The runner is configured to interfere with the formation of the e-script by being positionable at the formation point of the e-script. However, the runner disclosed in Jensen has many flaws. First, as is shown in FIG. 2, runner 11 is shaped and sized such that it can fall into the retainer ring Ref: 4, whereby the runner can become lodged below the retainer ring. Further, the weight of the runner can negatively produce significant downward force in the welding wire when the first container is exhausted. This is especially true since the runner disclosed in Jensen has a central passage configuration that prevents the runner from being removed from the welding wire without cutting the welding wire or destroying the runner. For these reasons and other reasons, the Jensen device fails to effectively overcome the natural problems with creating an endless wire system.
In order to work in connection with the wire feeder of the welder, the welding wire must be dispensed in a non-twisted, non-distorted and non-canted condition, which produces a more uniform weld without human attention. It is well known that wire has a tendency to seek a predetermined natural condition which can adversely affect the welding process. Accordingly, the wire must be sufficiently controlled by the interaction between the welding wire package and the wire feeder. To help in this respect, the manufacturers of welding wire produce a wire having natural cast, wherein, if a segment of the wire was laid on the floor, the natural shape of the wire would be essentially a straight line; however, in order to package large quantities of the wire, the wire is coiled into the package, which can produce a significant amount of wire distortion and tangling as the wire is dispensed from the package. As a result, it is important to control the payout of the wire from the package in order to reduce twisting, tangling or canting of the welding wire. This condition is worsened with larger welding wire packages which are favored in automated or semi-automated welding.
The payout portion of the welding wire package helps control the outflow of the welding wire from the package without introducing additional distortions in the welding wire to ensure the desired continuous smooth flow of welding wire. Both tangling or breaking of the welding wire can cause significant downtime while the damaged wire is removed and the wire is re-fed into the wire feeder. In this respect, when the welding wire is payed out of the welding wire package, it is important that the memory or natural cast of the wire be controlled so that the wire does not tangle. The memory or natural cast of the wire causes a constant force in the convolutions of wire which is directed outwardly such that the diameter of the convolutions is under the influence of force to widen. The walls of the wire welding package prevent such widening. However, when the welding wire is payed out of the package, the walls of the package lose their influence on the wire, and the wire is forced toward its natural cast. This causes the portion of the wire which is being withdrawn from the package to loosen and tend to spring back into the package, thereby interfering and possibly becoming tangled with other convolutions of wire. In addition to the natural cast, the wire can have a certain amount of twist, which causes the convolutions of welding wire in the coil to spring upwardly.
The payout device, braking devices or retainer ring are positioned on the top of the coil and forced downwardly against the natural springing effect of the welding wire. The downward force is either the result of the weight of the retainer ring or a separate force-producing member, such as an elastic band connected between the retainer ring and the bottom of the package. The wire is directed through the retainer ring in a designated manner to control its outward flow. With respect to the downward force of the ring, the optimal downward force during the shipment of the package is different than the optimal downward force for the payout of the welding wire. Accordingly, while elastic bands or other straps are utilized to maintain the position of the payout or retainer ring during shipping, the weight of the retainer ring can be used to maintain the position of the payout relative to the wire coils during the payout of the wire. However, the braking device must descend within the package as the wire is unwound from the wire coil.
As can be appreciated, it is preferred that any device utilized to transform a welding wire container into an endless wire system should be capable of functioning with existing welding wire technology and new welding wire technology. In this respect, and is as discussed above, braking devices or rings are utilized to control the unwinding of the wire from the wire coil. It is important that the wire be controlled to minimize tangling or any other form of interruption of flow of the welding wire. These braking devices have evolved over the years, and devices such as is disclosed in Cooper have been found to be effective. Therefore, the ability to utilize existing brake ring technology is an advantage.
The welding wire can also be controlled by other mechanisms such as the packaged beads, as is shown in Chung. The packaged beads along with pressing pipes help control the out flowing welding wire as it exits the wire drum. Again, endless wire systems configured to work with existing technologies that have been proven to provide tangle-free wire dispensing is an advantage.